GRAHAM — A Burlington man pleaded guilty Thursday to second-degree murder, stabbing and killing his friend in a parking lot brawl in 2011, and was sentenced to at least 12 years in prison.

Rondale Lamar Langston, 22, was killed June 13, 2011, when then-20-year-old Khalid Khaquan Onion stabbed him once, piercing his heart. Onion, now 22, also injured Langston’s brother, William Deontrey Langston, during a fight that broke out in the parking lot of Beaumont Court Apartments in Burlington.

He fled before Burlington police arrived but turned himself in two days later.

Onion was close friends with the brothers. Their mother, Tonya Langston, told the court Thursday she considered Onion a son and was devastated by the crime. Watching Onion be sentenced was like losing another son, she said. She told him twice that she loved him and that she’d forgiven him for the murder.

Alamance County Assistant District Attorney Paul Soderberg recounted the facts of the case Thursday for Superior Court Judge Wayne Abernathy.

Burlington police were called to the Beaumont Court Apartments twice the evening of June 13, 2011. The first call was concerning a disturbance at the apartments, which involved Onion, William Langston and another Langston brother.

Soderberg said the three were arguing about gang-related issues and personal matters. Onion and William Langston agreed to a fist fight to settle the dispute but the fight was called off when Onion pulled a knife.

When Burlington police arrived in response to that incident, the parties had dispersed. Burlington police cleared the scene at 6:40 p.m.

The situation quickly re-escalated. Rondale Langston heard about the knife pulled on his brother and confronted Onion. A fight began between the two. William Langston ran to the scene to defend Rondale Langston. Onion used the knife on the men during the fight, stabbing Rondale Langston in the chest and cutting William Langston on the hand and back.

Police were called back to the apartments at 6:45 p.m. Rondale Langston was found on a couch in a nearby apartment. He was declared dead only minutes later at Alamance Regional Medical Center.

Onion was indicted on first-degree murder and assault with a deadly weapon inflicting serious injury. Soderberg said he agreed to the plea to a mitigated second-degree murder sentence because the Langston family didn’t want to have to go through a trial.

Witnesses in the case had also disappeared or changed their stories, Soderberg told Abernathy.

Defense attorney Rob Sharpe stipulated to the facts of the case and said little during sentencing “out of respect for the family” and its suffering.

Abernathy issued a mitigated sentence, finding that Onion turned himself in and admitted responsibility early in the investigation. Abernathy sentenced him to between 144 to 182 months in prison, a minimum of 12 years and a maximum of 15 years, 2 months.